Breech block mechanism



April 16, 1946. w. SUMMERBELL BREECH BLOCK MECHANISM Filed May 16, 1941` 2 sheets-shea 1 11: wllflhnwnnuunn. A .9 5

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- mvENToR Willi am Sum 'm erh all BY 97V( c K f ATTORNEYS pl 16, 1945 w. SUMMERBELL 2,398,453

BREECH BLOCK MECHANISM Filed May 16, 1941 2 Sheets-Sheet 2 INVENTOR 48 J/ 52 56 J3 4a 43 William Summerfhell Patented Apr. 16, 1946 oFFlce nRsEcH'LooK MEC ilivl',sisi l Y Wiuiain summerbeu, watiyuegnjy. Appicatm'tiay is, lsnfese'riai.Ndgsa'icl (Granted under the Vact ofjMarch-3,18'83 as amended April'30z 1928;k 370 O. Gr.75?)rv The invention described hereinmay be manu,-

factured and used by or for the Government, for governmental purposesjwithout the payment to me of any royalty thereon. This invention relates {to a breechblock operating mechanism for a semi-automatic gun of the type having 'a verticallyv slidingv breech block.

It is the object of this invention to provide a compactv blockV operating mechanism which is largely on or forward of the breech ring whereby the gun may be mounted and operated in restricted quarters. v

It is a, further object to simplify assembly and maintenance of the breech mechanism and associated parts.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodi ment as shown in the accompanying drawings in which: f f v Figure 1 is a left side elevation of the device of this application, partly in section. 1

Figure 2 is a rear end elevation with th bracket sectioned on the line 2-2 of Fig. 1.

Figure 3 is a left side elevation of a portion of the mechanism sectionalized on the line 3 3 ofy Fig. 2 with the bracket removed.

Figure 4 is a right side elevation.

Figure 5 is a top plan View.

Figures 6 and 7 are respectively plan and side elevations of the breech operating crank.

Figure 8 is a side elevation of the operating shaft. f

Figure 9 is a detailed sectional View of the block operating camI and its supporting bracket taken on the line 9 of Fig. 4. f

Figure 10 is an enlarged detailed plan View of the drag link retaining pin.

Figure l1 is an enlarged elevation, partly in section of the lever, drag link, and retaining pin.

Referring to the drawings by characters of reference, Figure 1 shows a breech ring I in which a breech block 2 is vertically slidable. Depending portions 3 and 4 of the breech ring are bored to provide bearings for the block operating shaft 'I (Fig. 8). The shaftis provided with a laterally extending lever B and with bearing surfaces 9 and I0 to be journaled in thebreech lugs at 3 and 4. The central portion of the shaft 1 is adapted to receive the crank II (Figs. 6 and 7), being pro-V vided with keys I2 to engage the key slots I3 in theV end of the crank. l

The breech block 2 is slidable in a known manner in the breech ring and is vformed in its lower portionfwith a. transverse T-shaped slot I4 ex-` tendinglfro'm the lfront to the rear faces of the block and having the leg I5 of the T slot intersecting the lower face of the blockas best shown inFigsr2 and 3. The breech block is further provided with rearwardly extending stops I6 for engaging notches I1 in the breech ring to limit the upward movement of the block.

' The crank I I (Figs. 6 and '7) comprises a hollow cylindrical portion; I8 adapted to` be mounted on the shaft 'I as described above and having a. central upwardly extending arm I9 provided at its extremity with blockengaging lugs 20 complemental .to the T-shaped slot in the block. This arm I 9 is further provided with a rearwardly extending handle 2I having alateral grip portion 22. The crank is further provided with'a downwardly extendingA stop portion 23 adapted to engage a lug 26 on the breech .ring *and at the end opposite Itheabove mentioned key slots I3 with an voperating arm 24 provided on its lower extremity with a cam-engaging lug 25.

The, block is inserted into the breech ring from the bottom with thel block-engaging lugs 2l) within the T slot I4 of the breech block and the shaft I is inserted through its bearings in engagement with the cylindricalv portion I8 of the operating crank'. It will be seen that the crank is free to rotate inthe lbreech ring `within the limits mposed by the stops I1 and 23' and that this rotary motion is translated by engagement of the lugs Ztl-.with the T-shaped slot I4 into vertical reciprocating motion of the breech block. The handle 2I .hasfbeen providedk in order that the block may be manually operated if desired. It will be noted that the handle'is located under the breech block where it may be readily reached when it is desired to operate the block manually. At the same time the handlev is out of the way and will not interfere with service of the piece in normal semi-automatic re from a mount in restricted quarters as in av tank. Guns having handles protruding from the sides of the breech ring cannot be conveniently y used in tanks because of thehandle interference.

A springv housing 21 has been provided on the left side of the breech ring for the reception of a co'unterbalancing and closing spring 28, A longitudinal bore y29v in the breech ring serves as a guide for the crosshead 30 on the end of the rod13l. A reduced portion on the front end of the crosshead member provides a seat for a spring bushing 32; The spring 28 is conned on the rod between thebushing 32and a spring follower 33, retainedpngthe endxof the Yrod by a keyed nut f pin 39 (see Fig. 11)'.

34. The slotted end of the crosshead is provided with a drag link 35. It will be noted that the spring, rod, and drag link can be assembled as an independent unit and as such insertedin the spring case from the front. A hole 36in the crosshead and a cooperating hole, not shown, in the guide member. 29. are providedim order that Y a pin maybe insertedfto temporairllgjretainetle crosshead with the spring in slightly compressed relation. 'Ille end of the drag link 35 is provided' movement by the engagement of the head 56 with the surface of the boss 5I. The cam plate may be released and removed for replacement or rewith a hole 38 to cooperate with a hole 31 through the lever 8 foryreception of a Vretainingpi'n- 38 (Fig. 10). A keyway 40 is formedl in hole 3l and a similar keyway 4l is formed in hole 378' (see 11) to allow the passage of a keyj 42 -forme`d on` the central drag link-engaging portion. yofA the which the crosshead is temporarily retainedbya Only in theV position in pin in hole 36 are the two keywaysmandi Il: in"

alignment in order that the pin may be inserted through hole 31 with the'key' 42 engagingthe'key.I way 4I in the drag link. In any other position the key 42 being in enga'gementwiththev drag link will have been rotated toa positionvv in whichA it is opposed bythe-'inner surface offthelever'as in Fig. 11. It will be noted that as the leverv is rotated in clockwise direction thev amount ofvan'- gular travel required for a given amount of' reciprocation of the crosshead will beprogressl'vely increased.V Similarly the resistance'i of the spring will increaseas it is compressedv by the-recipro-A cation of the rod. As` theV mechanical advantage is thus increasing in practically the same ratio 'as' the spring tension isiA increasing a substantially uniform force'will beap'pliedtendingto raise the breech block to 'closed position. Y

' An extractor mechanism such as--that shown in mycopending application, Serial No. 393,763, may be provided to' extract the fired cases and torre-v tain 4the breech block'in'open position until'Y re-l leased by the insertion of'afresh round 'cit` am@v .Y

munition.

A bracket 43-15 attachent@ 'e fixed percef'the gun carriage, vfor example, thelcradle (-Figs; 11 and 4) and provided with a longitudinal track, V44 cooperating with a guide rail 45 attached? to the breech ring., The track i and guiderail- 45" may be formed inA` any desired manner whichlw-ill allow the rail to slide-longitudinallyof? the track-1 in the bracket and atfthe` sameztime willsupport the bracket againstve'rticjal andfrlateral displace'- men-t. The bracketA is provided; witlraanaupper cam surface 46 attached: to the face. otthebracket n by bolts or the like andwith azlower'cam; plate:

41..v Thebracket is provided withv externalstiffeniing ribs 43 and with cam' supporting flanges' 490 and 50 against which therlower .cam 41 is. releas-fv ably. mounted, Figs. 1-4 and 9,.. The bracket'hasl been provided on its outer. surface. with. aff-boss? 5l in which parallel intersectingfboresf 52 and' 63 have been formed (Figs. 4 and 9).. A screw-'5.4i having an enlargedshan-k =and head- 56, is:

' secured to the carnplate4lv (fFig. 9). The` diameter of theV shank issuch that. itengages.V with. the smaller'diarneter bore 5- 2lwhen the .cam-.plate is ,in engagement with the supporting. flanges. The diameter of the bore 53 issuch thatwhenthe cam is moved forwardly the. head, 56'. will pass'` freely through the bore. A plungerf51'andlrspri`ng,

5.3 are secured in the cam platef 4.1; by a bushing, 59. (Figs. l and 4)'.` .When the. camfplate. is'i'nA position against the ysupportingl flangesr the, plunger 51. engages aY hole 6Il` inthe supporting'1 flange 5I!` to retain the'. canifplatev against fbrvfard. motion,the plate bei'ngv secured against" "lateral pair by depressing the plunger 51 with a suitable instrument and sliding the plate forward on the bracket as shown in Figure 9.

Itwill'V be :observed thatfwhen theebiiacket is mounted; thefcarn-engag'ingg lug 2 ifdnathe operating arm 24 will be in position to engage Vthe track formed between the camplates. As the gun recoils on its mount during firing the-lug 25 will be' lifted between the cam plates and will serve to rotate the block-operating crank in clockwise direction (Fi'gjl) to open the breech. As explained before the'block will be retained in open position by the extractor mechanism and as the gun returns to battery the. lug 25 will be carried forward; abovetheupper cam plate 46 which terminates short of the forward position of the lug. While the upper cam plate is not directly concerned inthe operation of themechanism'it does fill a very' important functiony in that it prevents any bouncing or erratic action due to the resiliency of the operating arml and thelug 25 which on being transmitted to the extractor mechanism 'might result infaulty ejection. When a new round is inserted', its engagement with the extractor fingersjwill release the breech block which will-close atonce` under the v*force of the spring upon the crankshaft arm.

Obviously theI operation of the breech mechanism at high'recoil velocities imposes a severe Y the breech ring in battery position. The operating mechanism 'is' thus compact and does not interfere with the movements of the gunners in service of the piece. Further the dragging action of the operating armfcausesfthe operation of the mechanism to be smoother. The operating mechanism does not involve any screws, nuts, bolts, or cotter pins as fastening means in parts which may need toY be disassembled in normal operationof the: gun. The only toolneededto disassemble the mechanism isa nail or drift pin and disassembly has been effectedv only with the aid of a match stick. V

' Iclaim: r Y A l. In. agun, a. breech ring and avertically slidable breech block therein, abreech operating mechanism comprising a shaft journaled inthe breech ring, acrank member on and constrained to rotate with said shaft and having an arm engaging the breech block for operation thereof,

a leverron an end of the shaft having a keyslottedbore,.a drag link having a similar key slotted borev in one end thereof, a drag link retaining pin havinga key on the drag link engaging portion of its shank complemental tothe key slotvin the drag linkand. insertable through the key slot in the lever. only inthe position inV which the key slots in lever and drag link Aare in register, and spring means engaging the other end of the drag link whereby the breech block will beconstrained to closed position, in. whichposition-said key slots do. not register..

2.- An operating cam for an automatic breech mechanism comprising a bracket plate adapted to be secured at its forward end to a gun cradle, a forwardly facing abutment at the rear end of the inner face of said plate, an upwardly facing abutment at the bottom side of the inner face of said plate, a recessed replaceable cam plate engaging said abutments, and a spring-backed plunger in said recess having a portion engaging said upwardly facing abutment to maintain the cam plate in engagement with said abutments.

3. In a breech closing mechanism, a breech ring reciprocable in recoil and counterrecoil, a breech block vertically movable in the ring, a longitudinally extending bracket adapted for attachment to a gun cradle and provided with a longitudinal track, a guide rail on the breech ring entering said track, said bracket having a cam plate secured thereto having an upwardly facing cam surface, an operating shaft rockably mounted in the ring and extending transversely thereof and provided with an operating lever outside of said ring, a sleeve mounted on said shaft for movement therewith, the sleeve being provided with an arm having continuous operative engagement with the breech block to reciprocate said block, an arm in engagement with said cam surface to open the breech block upon recoil of the ring, a stop arm constructed and arranged to engage a portion of the ring to limit the opening movement of the breech block and an arm extending rearwardly beneath the breech ring for manually rocking the operating shaft to open or close the breech block, means carried by the bracket and cooperating with the cam engaging arm on said sleeve to positively hold the breech block open during counterrecoil of the breech ring, a spring carried by the breech ring for automatically returning the breech block to closed position after a round is chambered, and a pivoted link connecting said spring and said operating lever, whereby the spring is energized upon the recoil of the breech ring,

4. In a breech closing mechanism, a breech ring reciprocable in recoil and counterrecoil and provided with a longitudinal guide rail, a breech block vertically movable in the ring, a bracket provided with a longitudinal track receiving said guide rail to guide said ring in its reciprocating movements, said bracket being adapted for attachment to a gun cradle and having upper and lower cam plates secured thereto, the lower plate having an upwardly facing cam surface terminating at its outer end in a straight surface substantially parallel to said track, the upper plate having a downwardly extending cam surface facing the cam surface of the lower plate and forming between them a cam track, the upper cam plate having an upper straight surface substantially parallel to said track, an operating shaft rockably mounted in the ring and extending transversely thereof and comprising an operating lever, a spring carried by the breech ring and having operative connection with the lever Whereby the spring is tensioned during recoil of the breech ring, an arm on the operating shaft having continuous operative engagement with the breech block to reciprocate the same, and another arm on the operating shaft having a portion constructed and arranged to enter said track and engage the said cam track during recoil of the ring to open the breech block and to thereafter engage the straight upper surface of the lower cam plate to positively hold said breech block open on its way to battery during the counterrecoil movement of the ring,

5. In a breech closing mechanism, a breech ring reciprocable in recoil and counterrecoil, a breech blo-ck vertically movable in said ring, a longitudinally extending bracket adapted for attachment to a gun cradle, means mounting the breech ring on the bracket for longitudinal sliding movement thereon, an upper and a lower cam plate on the bracket, the lower plate provided with an upwardly facing cam surface and a straight upwardly extending surface at its rear end parallel with the axis of the breech ring, the upper cam plate being provided with a downwardly facing cam surface which, with the cam surface of the lower plate, forms a track between said plates, the upper plate being provided with an upwardly facing surface also substantially parallel with the axis of the breech ring, an operating shaft rockably mounted in the breech ring and extending transversely thereof and provided with an operating lever, said shaft having a plurality of arms mounted thereon for rotation therewith, one of said arms having continuous operative engagement with the breech block to reciprocate the block, and another of said arms constructed and arranged to engage the cam surface of the lower cam plate during recoil of the ring to open the breech block, and to thereafter engage the straight surface of the lower cam plate to positively hold the breech block open on its way to battery during counterrecoil movement of the ring, a stop arm on the operating shaft for engagement with the breech ring to limit the opening movement of the breech block, a spring carried by the breech ring for automatically returning the breech block to closed position after a round of ammunition is chambered in the ring, and a link means pivotally connecting said spring to the operating lever whereby the spring is energized upon recoil of the breech ring.

WILLIAM SUMMERBELL. 

